Simulation on co-gasification of bituminous coal and industrial sludge in a downdraft fixed bed gasifier coupling with sensible heat recovery, and potential application in sludge-to-energy

The co-gasification of bituminous coal (BC) and industrial sludge (IS) in the downdraft fixed bed gasifier (DFBG) was simulated by a validated steady-state model structured using the Aspen Plus software. The gasification process was decoupled into the drying, pyrolysis, partial oxidation, and reforming and reduction, and then modeled. Furthermore, the sensible heat recovery of syngas was also considered to realize the energy optimization of DFBG gasification system. The sensitivity analysis was performed to investigate the influences of the gasification temperature, air equivalent ratio, and steam to BC-IS blends ratio (S/BC-IS) on the co-gasification characteristics. The energy distributions of the whole process were completed by calculating energy input and output. Results showed that, boosting gasification temperature could improve the syngas content and gasification performance. However, as air equivalent ratio increased, the H2 and CO contents, and gasification performance constantly reduced. A higher S/BC-IS was beneficial for H2 production, but impaired CO content and cold gas efficiency. In addition, the calculations of energy balance indicated that the best cold gas efficiency of the blends could be obtained when the BC blending ratio was 0.7.